This invention relates to protective inner soles for foot wear. More specifically, this invention relates to a cushion inner sole providing a substantially increased degree of comfort and protection against foot injury during strenuous running and jumping.
One of the chronic problems faced by athletes and others who engage in strenuous or persistent running, jumping or walking is the development of blisters and bruises on the soles of the feet. The cause of blistering is often the frictional sliding of the foot surface within the shoe across the surface of the inner sole. Blistering most often occurs at those points on the foot where maximum force or pressure is applied during abrupt changes of direction. These points are most commonly under the metatarsal head and under the great toe.
A standard approach to overcoming these problems is in the provision of a pad or liner within the shoe generally referred to as an inner sole. A wide variety of materials and combinations of materials have been proposed and used in the construction of inner soles. Probably the most successful and widely used of such materials are the elastomeric foams. For example, U.S. Pat. No. 3,448,533 discloses an inner sole having a base ply of fiberboard or like material, a cushion ply of a foamed polymeric thermoplastic resin and a flexible cover ply which provides a foot contact surface.
Another approach to the use of elastomeric foams for inner soles is shown in the Spence patent, U.S. Pat. No. 3,449,844. This patent discloses an elastomeric foam base layer covered with a two way stretch fabric such as stretch nylon. The stretch fabric is adhesively bonded to the base ply and provides a slick surface between the inner sole and the user. While these prior art approaches to inner sole construction do provide a substantial cushioning effect which alleviates much of the problem of foot bruising, the problem of frictional blistering caused by the relative movement of the foot across the surface of the inner sole is still present.